Affiliation: Free Radical Research Center and Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI, USA.

ABSTRACT

Background: Recent research has revealed that targeting mitochondrial bioenergetic metabolism is a promising chemotherapeutic strategy. Key to successful implementation of this chemotherapeutic strategy is the use of new and improved mitochondria-targeted cationic agents that selectively inhibit energy metabolism in breast cancer cells, while exerting little or no long-term cytotoxic effect in normal cells.

Results: Both Mito-ChM and Mito-ChMAc selectively depleted intracellular ATP and caused prolonged inhibition of ATP-linked oxygen consumption rate in breast cancer cells, but not in non-cancerous cells. These effects were significantly augmented by inhibition of glycolysis. Mito-ChM and Mito-ChMAc exhibited anti-proliferative effects and cytotoxicity in several breast cancer cells with different genetic background. Furthermore, Mito-ChM selectively accumulated in tumor tissue and inhibited tumor growth in a xenograft model of human breast cancer.

Conclusions: We conclude that mitochondria-targeted small molecular weight chromanols exhibit selective anti-proliferative effects and cytotoxicity in multiple breast cancer cells, and that esterification of the hydroxyl group in mito-chromanols is not a critical requirement for its anti-proliferative and cytotoxic effect.

Figure 2: Effects of Mito-ChM on colony formation in MCF-7, MDA-MB-231 and MCF-10A cells. (A) MCF-7, MDA-MB-231 and MCF-10A cells were treated with Mito-ChM (1–10 μM) for 4 h and the colonies formed were counted. (B) The survival fraction was calculated under the same conditions as in (A). Data shown represent the mean ± SEM. *, P < 0.05, **, P < 0.01 (n = 6) comparing MCF-7 and MDA-MB-231 with MCF-10A under the same treatment conditions.

Mentions:
We used a clonogenic assay to monitor the anti-proliferative effects of Mito-ChM. As shown in Figure 2A, there was a dramatic decrease in colony formation in MCF-7 and MDA-MB-231 cells, as compared to MCF-10A cells, when treated with Mito-ChM (1–10 μM) for 4 h. Figure 2B shows the calculated survival fractions of MCF-7, MDA-MB-231 and MCF-10A cells. Mito-ChM significantly decreased the survival fraction in MCF-7 and MDA-MB-231 cells as compared to MCF-10A cells. Notably, the colony formation data indicate that a 4 h treatment with 3 μM Mito-ChM was sufficient to induce significant anti-proliferative effects in both MCF-7 and MDA-MB-231 cells without noticeable cell death under those conditions (Figure 1A). Taken together, we conclude that a 4 h treatment with 3 μM Mito-ChM was sufficient to inhibit cancer cell growth, without directly causing cell death at this time point.

Figure 2: Effects of Mito-ChM on colony formation in MCF-7, MDA-MB-231 and MCF-10A cells. (A) MCF-7, MDA-MB-231 and MCF-10A cells were treated with Mito-ChM (1–10 μM) for 4 h and the colonies formed were counted. (B) The survival fraction was calculated under the same conditions as in (A). Data shown represent the mean ± SEM. *, P < 0.05, **, P < 0.01 (n = 6) comparing MCF-7 and MDA-MB-231 with MCF-10A under the same treatment conditions.

Mentions:
We used a clonogenic assay to monitor the anti-proliferative effects of Mito-ChM. As shown in Figure 2A, there was a dramatic decrease in colony formation in MCF-7 and MDA-MB-231 cells, as compared to MCF-10A cells, when treated with Mito-ChM (1–10 μM) for 4 h. Figure 2B shows the calculated survival fractions of MCF-7, MDA-MB-231 and MCF-10A cells. Mito-ChM significantly decreased the survival fraction in MCF-7 and MDA-MB-231 cells as compared to MCF-10A cells. Notably, the colony formation data indicate that a 4 h treatment with 3 μM Mito-ChM was sufficient to induce significant anti-proliferative effects in both MCF-7 and MDA-MB-231 cells without noticeable cell death under those conditions (Figure 1A). Taken together, we conclude that a 4 h treatment with 3 μM Mito-ChM was sufficient to inhibit cancer cell growth, without directly causing cell death at this time point.

Affiliation:
Free Radical Research Center and Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI, USA.

ABSTRACT

Background: Recent research has revealed that targeting mitochondrial bioenergetic metabolism is a promising chemotherapeutic strategy. Key to successful implementation of this chemotherapeutic strategy is the use of new and improved mitochondria-targeted cationic agents that selectively inhibit energy metabolism in breast cancer cells, while exerting little or no long-term cytotoxic effect in normal cells.

Results: Both Mito-ChM and Mito-ChMAc selectively depleted intracellular ATP and caused prolonged inhibition of ATP-linked oxygen consumption rate in breast cancer cells, but not in non-cancerous cells. These effects were significantly augmented by inhibition of glycolysis. Mito-ChM and Mito-ChMAc exhibited anti-proliferative effects and cytotoxicity in several breast cancer cells with different genetic background. Furthermore, Mito-ChM selectively accumulated in tumor tissue and inhibited tumor growth in a xenograft model of human breast cancer.

Conclusions: We conclude that mitochondria-targeted small molecular weight chromanols exhibit selective anti-proliferative effects and cytotoxicity in multiple breast cancer cells, and that esterification of the hydroxyl group in mito-chromanols is not a critical requirement for its anti-proliferative and cytotoxic effect.